Combustion is the oldest process employed by mankind for the conversion of energy from a variety of solids and liquid carbonaceous and hydrocarbon materials. The energy content of such materials is converted into heat that in turn is used for a number of energy applications (heating, cooling, power generation, propulsion, etc.).
Only recently, partial oxidation of certain solid and liquid materials has been pursued to make fuel gases that could in turn be used by advanced energy conversion technologies such as Gas Engines (GEs), Gas Turbine Combined Cycle (GTCC) plants and ultimately, in the future, fuel cells. Partial oxidation may provide enhanced thermal efficiencies and significantly reduced pollution performance of the process while enhancing the economics. In partial oxidation, the material is burned with less oxygen than what is required to achieve complete combustion. The energy in the material is released as sensible heat as well as energy content of combustible gases and condensable hydrocarbon products. The ratio between the amount of sensible heat in the product gas to cold product gas calorific value is typically significant since partial oxidation is primarily an incomplete combustion process.
In contrast to combustion and partial oxidation, pyrolysis typically is carried out at a lower temperature and in the absence of air or other oxidants. Pyrolysis is similar to destructive distillation in which gaseous fuels and a significant amount of vapors of liquid hydrocarbons can be derived from the feedstock. In pyrolysis, the carbon conversion is relatively low and the tar yield is relatively high.
Another method for converting carbonaceous materials into a fuel source is through endothermic conversion, such as by using steam reforming reactions. For example, various indirectly heated steam reforming processes are disclosed in U.S. Pat. No. 5,059,404, U.S. Pat. No. 5,133,297, U.S. Pat. No. 5,306,481, U.S. Pat. No. 5,536,488, and U.S. Pat. No. 6,548,197, which are all incorporated herein by reference. In the above patents, a fluidized bed may be heated, for instance, by a pulse combustor. Other patents which describe the use of a pulse combustor include U.S. Pat. No. 5,197,399, U.S. Pat. No. 5,205,728, U.S. Pat. No. 5,211,704, U.S. Pat. No. 5,353,721, U.S. Pat. No. 5,366,371, U.S. Pat. No. 5,638,609, and U.S. Pat. No. 5,842,289 which are also herein incorporated by reference. The steam reforming systems and processes disclosed in the above patents represent great advancements made in the art of treating carbonaceous materials; such as black liquors produced in the pulp and paper industry, coal, other biomass materials, and the like. Indirectly heated steam reforming processes offer low temperatures for the production of gaseous fuels consistent with a satisfactory level of carbon conversion and sulfur reduction. The present invention, however, is directed to further improvements in endothermic reforming processes.